Acetic acid, which is a fundamental chemical, is an important chemical widely useful in the petrochemical, polymer chemistry, organic chemistry, medicine, and pesticide fields. Among variously known methods of preparing acetic acid, particularly useful is the preparation of acetic acid through a methanol carbonylation reaction using carbon monoxide.
Conventional methods of preparing acetic acid through a methanol carbonylation reaction include 1) a Monsanto process mainly using rhodium (Rh), commercialized in the 1960s [Patent Document 1]; 2) a Cativa process mainly using iridium (Ir), commercialized in the 1990s [Patent Documents 2 to 4]; and 3) an Acetica process using a heterogeneous catalyst configured such that a rhodium (Rh) catalyst is immobilized on a polymer [Patent Documents 5 to 7]. Although the above processes are satisfactory in reactant conversion and selectivity, they suffer from the aspect of use of energy, i.e. the consumption of a large amount of energy for the separation process for catalyst recycling and for the byproduct treatment process. In particular, the Monsanto and Cativa processes using the homogeneous catalyst in which catalyst recycling is limited are regarded as unprofitable at present, and the Acetica process using the heterogeneous catalyst is receiving a great deal of attention, and thus the number of research reports related thereto is gradually increasing.
Taking into consideration the fact that a methanol carbonylation reaction is carried out in a liquid state, the Acetica process is advantageous because the loss of the catalyst may be minimized due to the physical adsorption of the rhodium precious metal onto the polymer support. However, with regard to the heterogeneous catalytic reaction using the polymer support, there has been reported that the activity of the catalyst is slightly decreased compared to the homogenous catalytic reaction. Recently, the use of a support having a structure of activated carbon or hydrotalcite in lieu of the polymer support has been proposed. [Patent Document 8]
Also, thorough research is ongoing into minimizing the loss of rhodium precious metal and controlling the interaction between the rhodium active component and the support to thus increase the stability and dispersibility of the catalyst. In this regard, Non-Patent Document 1 discloses a technique for immobilizing, on the support, a rhodium complex using 3-benzoylpyridine as a functional group for optimizing the rhodium-support interaction.